Internal combustion engines will often not perform well as the temperature of the air supplied to the carburetor falls below certain temperatures. For example, engine efficiency may decrease because the fuel may not mix properly with the air and ice may form in the carburetor. To improve engine performance and eliminate carburetor icing, preheated air having a temperature greater than the ambient air temperature is supplied to the carburetor. The supply of preheated air is sometimes regulated because engine performance may also decrease, including problems with power losses and vapor lock conditions, if the air supplied to the carburetor is too warm.
Various systems are known which provide preheated air to the air inlet to the carburetor. In some systems, a housing may be provided having two inlets and an outlet to the air inlet of the carburetor. In those systems, one inlet to the housing is typically connected to a source of ambient air and the other inlet to the housing is connected to a source of preheated air. In some of these systems, the relative amounts of ambient air and preheated air which enter the carburetor are adjustable. Some systems are manually controlled and others are automatically controlled.
One problem with some manual systems is that there is often only a two position switch on the housing which must be manually moved as the temperature of the ambient air changes. Failure to properly move the switch can cause problems affecting engine performance if the air entering the carburetor is either too warm or too cold.
Some of the automatic systems vary the relative amounts of ambient air and preheated air which enter the carburetor by positioning a door or flap in the housing in varying positions depending upon the air temperature sensed. Some previous systems employ a rotatably mounted door which pivots on a vertical axis of rotation parallel to a major surface of the door and located adjacent at an edge of the door. One problem with this type of system is that extra space must be provided within the housing to accommodate movement of the door about its axis of rotation between the various positions.
Another problem with some automatic systems is that they may employ intricate structure to regulate the amount of ambient air and preheated air supplied to the carburetor. For example, some prior systems employ pneumatically operated devices to move a door or doors to regulate the ambient air supply and the preheated air supply. Often the pneumatically operated systems employ temperature sensing devices to operate the pneumatic controls.
Some additional problems with some prior preheat systems occur when the internal combustion engine is used in connection with a generator set. A generator set generally includes an internal combustion engine which drives a generator for producing electrical energy to provide a self-contained power source. Often generator sets are provided as auxiliary power sources in applications such as recreational vehicles and ambulances. One consideration often emphasized with generator sets used in these applications is to minimize the size of the generator set while providing a preheat system that is simple to manufacture and to operate. Many existing preheat systems have bulky and complex door mechanisms and control mechanisms to move the door mechanisms to regulate relative amounts of ambient air and preheated air. Further, in some of these prior systems the preheated air supply employs an extra tube or duct which draws air heated by a specific portion of the engine and directs it into the housing and to the carburetor. The ambient air supply may in some instances employ a duct or tubing to draw ambient air from a particular location.
It is clear that there has existed a long and unfilled need in the prior art for a preheat system that automatically and variably regulates the temperature of air supplied to the carburetor without requiring excessive space or involving intricate structure. In addition, there is a need for an automatic preheat system for use on a generator set that does not significantly increase the size of the generator set nor involve complex and intricate parts. The present invention solves these and other problems associated with the prior art.